The Molecular Genetic Unit
Structure of DNA
· Contributions of Scientists
o Meischer, Griffith*, Hammerling, Chargaff, Hershey and Chase*, Franklin, Watson and Crick Who was responsible for discovering bacterial transformation?
· Structure of a Nucleotide How do various nucleotides differ?
· Structure of a DNA molecule What is meant by 5’ and 3’ ends of the molecule?
DNA Replication
· Meselson and Stahl – Semiconservative Replication Why was only one band found after one round of replication?
· The process of DNA replication
o 6 enzymes and a binding protein What is the role of DNA gyrase? DNA ligase?
· PCR Compare PCR to natural replication.
Protein Synthesis
· Contributions Garrod, Beadle and Tatum, Ingram
o (Gene – Protein relationship) What is meant by the “One gene-One polypeptide Hypothesis”?
· Central Dogma Why is this so important to biology?
· RNA and ribosomes Describe how the three types of RNA differ.
· Transcription List the four steps of transcription.
· Translation What is special about stop codons?
Mutation
· Types and examples Why is it likely that most mutations are neutral?
Self Quiz
Chapter 4 all
Chapter 5 eliminate 7
Chapter 6 Do 1, 5, 7, 10 –13
Part A Multiple Choice
1. The backbone of one strand of a DNA molecule starts at a deoxyribose sugar and ends at a phosphate group. This strand
a. is the coding strand.
b. is the template strand.
c. runs in the 3’ to 5’ direction.
d. runs in the 5’ to 3’ direction.
e. is unlikely to be transcribed into RNA.
2. The two strands of a DNA molecule are held together by
a. covalent bonds.
b. ester linkage.
c. glycosyl linkage.
d. hydrogen bonds.
e. phosphodiester bonds.
3. 22% of a DNA molecule is found to be thymine. What percentage of the molecule would be expected to be guanine?
a. 16%
b. 22%
c. 28%
d. 44%
e. 56%
4. Aside from the nucleus, which other organelles in the cell contains DNA?
a. Centrioles
b. Endoplasmic reticulum
c. Lysosomes
d. Chloroplasts
e. Ribosomes
5. Which of the following has an anticodon at one end and an amino acid acceptor site at the other.
a. cRNA
b. mRNA
c. mtRNA
d. rRNA
e. tRNA
6. Which of the following is combined with proteins and built into two different sized subunits in the nucleolus?
a. cRNA
b. mRNA
c. mtRNA
d. rRNA
e. tRNA
7. The new strand in DNA replication and the messenger RNA transcript are both built in the 5' to 3' direction.
a. True
b. False
8. Each gene is one complete DNA molecule.
a. True
b. False
9. Most of a human cell’s DNA is found in genes.
a. True
b. False
10. Many species have larger genomes (more base pairs) than humans.
a. True
b. False
11. During replication, the nucleotides that are added begin as a triphosphates.
a. True
b. False
Use the following options for questions 18 and 19.
light /
medium /
heavy /
light
heavy /
light
medium
a / b / c / d / e
12. Meselson and Stahl cultured E. coli in cultures with nitrogen-14 and nitrogen-15. First they grew the bacteria for many generations in cultures with nitrogen-15. When they isolated the DNA in density gradient centrifugation, which of the above patterns did they observe?
13. They then moved the bacteria to cultures that contained only nitrogen-14 and allowed one cycle of reproduction. When they isolated the DNA this time, what banding pattern did they find?
14. This experiment confirmed which of the following ideas?
a. DNA requires nitrogen for replication.
b. DNA replication is conservative.
c. DNA replication is semi-conservative.
d. Transcription is semi-conservative.
e. None of the above.
15. Which of the following enzymes is responsible for adding nucleotides to the growing DNA strand?
a. DNA gyrase
b. DNA ligase
c. DNA polymerase I
d. DNA polymerase III
e. RNA primase
16. Which of the following in PCR performs the same function as RNA primase?
a. Heat
b. Cooling
c. RNA polymerase
d. Primers
e. Taq polymerase
17. One way that eukaryote replication differs from prokaryote replication is
a. eukaryote replication is much simpler.
b. eukaryote replication occurs much faster.
c. eukaryote replication starts at many places in the genome.
d. eukaryote replication has been studied more and is better understood.
Part B Description Questions
1. List 3 key steps in the science that placed DNA at the center of modern biology.
2. Describe the process of DNA replication.
3. Where does replication occur in the cell cycle?
4. How is transcription similar to replication?
5. Describe the role of tRNA in protein synthesis.
6. How does the lac operon work?
Part C Explanation Questions
7. Compare the processes of DNA replication and transcription.
8. Why is most of our understanding of molecular genetics based on experiments with bacteria?
9. DNA and the Central Dogma are at the center of modern biology. Describe 3 key contributions by scientists and how they improved our understanding.
1c 2d 3c 4d 5e 6d 7a 8b 9b 10a 11a 12c 13b 14c
15d 16b 17c